The present invention relates to a sheet discharging tray device and an image forming system provided with the sheet discharging tray device.
What is commonly known in the prior art includes an image forming system. This image forming system is provided with an image forming apparatus using the electrophotographic process, and includes a sheet finisher for performing various forms of sheet finishing operations as required, and an intermediate conveyance device for conveyance of sheets between the image forming apparatus and sheet finisher.
The image forming system of this type includes a sheet discharging tray device equipped with a sheet discharging tray for loading sheets discharged from the sheet discharging section on the final stage of the system. To discharge a great number of sheets, this sheet discharging tray device is designed in such a way that the sheet discharging tray moves vertically in the sheet loading direction. To offset the sheet loading position for a prescribed number of sheets, the sheet discharging tray is swingably structured in the direction of tray shift.
For example, the Japanese Patent Application Publication No. 2008-189453 discloses a sheet discharging tray device wherein a plurality of sheets are conveyed at a prescribed speed at prescribed intervals and are discharged from a discharge outlet, and the sheets stacking on the sheet discharging tray are placed on a sheet discharging tray. This sheet discharging tray device performs tray shift operation wherein the sheet discharging tray is moved in the horizontal direction approximately perpendicular to the sheet discharge direction. This is to ensure that, after the continuously conveyed preceding sheets have been placed on the sheet discharging tray, the succeeding sheets conveyed after the preceding sheets will be placed at a position offset with respect to the position of the preceding sheets loaded on the sheet discharging tray. Here the tray shift operation is performed wherein the speed of the sheet discharging tray is reduced just before the completion of sheet discharging tray movement.
The sheet discharging tray device of this type has a problem in that a sheet alignment deviation is likely to occur due to the tray shift operation. Further, to ensure alignment performance, it is necessary to reduce the movement of the tray shift operation and to set an increased sheet distance between discharged sheets for the sheet tray. However, this may result in reduced productivity.
In view of the problems described above, it is an object of the present invention to perform tray shift operation by ensuring desired alignment performances and the maximum productivity.